1. Field of the Invention
This invention relates to a lubricant supplying unit for coating the surface of the track shaft with lubricant in a linear motion apparatus, for example, a linear guide unit and ball screw, in which a track shaft engages a slide member such that they are movable relative to each other through rolling bodies such as balls and rollers, and more specifically, to a linear motion apparatus using the same.
2. Description of the Related Art
Conventionally, this kind of the linear motion apparatus has been used in a linear guide section of a machine tool, transfer unit and the like, and includes a linear guide unit which is mounted on a fixing unit such as a bed and a saddle for guiding a movable unit such as a table and a ball screw which is used together with this linear motion unit for providing the above mentioned movable unit with the linear motion stroke depending on a rotation speed of a motor.
The former linear guide unit comprises a track rail (track shaft) which is disposed on the aforementioned fixing unit and in which rolling grooves for balls are formed in the length direction thereof, and a sliding base (sliding member) which has a load rolling groove opposing the rolling groove in the track rail through a plurality of balls and in which an infinite circulation path for the balls rolling in the load rolling groove is formed. This linear guide unit is so constructed that the sliding base supporting the aforementioned movable body carries out linear motion continuously along the track rail with an infinite circulation of the balls. On the contrary, in some cases, the track rail is so constructed to move relative to the fixed sliding base.
On the other hand, the latter ball screw comprises a screw shaft (track shaft) in which a spiral ball rolling groove is formed at a predetermined lead and a nut member (slide member) which has a load rolling groove opposing the ball rolling groove through a plurality of balls and in which an infinite circulation path for the balls rolling in this load rolling groove is formed. This ball screw is so constructed that the balls circulate in the aforementioned infinite circulation path with a relative rotation between the screw shaft and nut member and the nut member and screw shaft move relative to each other in the axial direction.
Upon use of these linear motion apparatuses, the balls, rolling grooves and the like need to be appropriately lubricated depending on a use condition in order to suppress wear of the balls themselves, rolling grooves of a track rail or screw shaft in which the balls roll and load rolling groove of a sliding base or nut member, and further maintain a high precision motion of the slide member for a long time.
Unexamined Published Japanese Patent Application No. 307442/1994 has disclosed a lubricant supplying system for supplying lubricant to balls, rolling grooves and the like. As shown in FIG. 22, in this lubricant supplying system, a pad 127 soaked in lubricant is accommodated within a cover frame 128 and the cover frame 128 is engaged with a track rail 129 so that the pad 127 inside comes into contact with the track rail 129. The cover frame 128 is mounted backward and forward with respect to the traveling direction of the cover frame 128 such that as the sliding base 130 moves, the aforementioned pad 127 comes into contact with the track rail 129. Therefore, if the sliding base 130 moves back and forth along the track rail 129, lubricant leaking from the aforementioned pad 127 is coated on the surface of the track rail 129 so that lubricant is supplied to the rolling grooves and balls.
However, because in the conventional lubricant supplying system, lubricant is applied to all the rolling grooves for balls provided in the track rail with a substantially single pad, there is a problem that lubricant cannot be applied equally to all the rolling grooves depending on a mounting posture of the track rail relative to the fixing unit such as a bed.
That is, lubricant is likely to flow vertically downward within the pad by its own gravity, for example, as shown in FIG. 23, if the track rail is mounted on the fixing portion 130 in a laterally fallen condition more lubricant is contained in the lower half portion of the pad. Therefore, although a sufficient amount of lubricant can be applied to the side face of the track rail positioned down, the sufficient amount of lubricant cannot be applied to the side face of the track rail positioned up, so that lubricant cannot be applied equally to all the rolling grooves.
Accordingly, the present invention has been made in viewpoints of these problems, and it is an object of the invention to provide a lubricant supplying unit preferable for a linear motion apparatus such as a linear guide unit, a ball screw unit and the like, always capable of coating all rolling body rolling grooves formed on a track shaft with an equal amount of lubricant regardless of a difference in the mounting posture of the track shaft with respect to a fixing unit, and more to provide a linear motion apparatus using the same.
That is, to achieve the above object, the present invention provides a lubricant supplying system mounted on a slide member engaging a track shaft through rolling bodies for applying lubricant to the track shaft with a relative motion between the slide member and track shaft, the lubricant supplying system comprising: a casing fixed to the slide member; a plurality of coating pieces which are protruded from plural positions of the casing so that they are in contact with the track shaft for coating the track shaft with lubricant; and lubricant accommodating chambers provided in the casing for supplying lubricant to the coating piece, wherein the plurality of the coating pieces are divided into groups comprising one or two or more adjacent coating pieces, and each group has a lubricant accommodating chambers.
The linear motion apparatus of the present invention comprises a track shaft in which rolling faces for rolling bodies are formed, a sliding member which engages the track shaft through the rolling bodies and slides relative to said track shaft, and a lubricant supplying member which is mounted on the sliding member for coating the surface of the track shaft with lubricant with such a relative motion, wherein the lubricant supplying member comprising a casing fixed to the sliding member, coating pieces which are protruded from plural positions of this casing such that they are in contact with the track shaft for coating the track shaft with lubricant, and lubricant accommodating chambers provided in the casing for supplying lubricant to the coating pieces, the plurality of the coating pieces being divided to groups consisting of one or two or more adjacent coating pieces while lubricant accommodating chamber formed dividedly for each group.
According to such a technological method, the plurality of the coating pieces for coating the track shaft with lubricant are protruded from the plural positions of the casing such that they are in contact with the track shaft and lubricant is supplied from the lubricant accommodating chamber in the casing to the coating pieces. As a result, if the sliding member moves relative to the track shaft, lubricant is coated to the surface of the track shaft by each coating piece.
According to the present invention, as the plurality of the coating pieces are divided to groups consisting of one or two or more adjacent coating pieces and the lubricant accommodating chamber is formed dividedly for each group, lubricant is only allowed to flow in the lubricant accommodating chamber of each group, thus it will not be concentrated on a particular position in the casing.
Thus, the amount of lubricant to be supplied to each coating piece can be substantially equalized, so that it is possible to coat the track shaft with constantly equal amount of lubricant unconcentratedly from these coating pieces.
Further, because in such linear motion apparatus using the lubricant supplying unit of the present invention, a substantially equal amount of lubricant is always coated to the track shaft from the plurality of the coating pieces regardless of the mounting posture of the track shaft, all the rolling bodies rolling on the rolling faces formed in the track shaft can be lubricated excellently, so that the motion accuracy of the sliding member relative to the track shaft can be maintained in an excellent condition for a long time.
From a viewpoint of equalizing the amount of lubricant to be supplied to each coating piece with such a technological means, it is preferable to divide the lubricant accommodating chamber corresponding to each coating piece.
Upon storing lubricant in the lubricant accommodating chamber, lubricant may be stored as it is. However, if considering ease of assembly of the unit, prevention of leak of lubricant and the like, it is preferable to place an absorbing body for absorbing and holding lubricant in the lubricant accommodating chamber.
Further, if lubricant held in the lubricant accommodating chamber is absorbed directly by the absorbing pieces, in case where the amount of lubricant in the lubricant accommodating chamber is still large, a large amount of lubricant is coated to the track shaft, while if the amount of lubricant in the lubricant accommodating chamber decreases, only a slight amount of lubricant is coated to the track shaft. Thus, it is difficult to coat the track shaft always with a constant amount of lubricant. Therefore, in such a viewpoint, it is preferable to provide with some oil amount control means for controlling an amount of lubricant to be supplied to the coating piece from the absorbing body.
Still further, in case where the lubricant supplying unit of the present invention mounted on a sliding base of a linear motion apparatus or a ball nut of a ball screw unit is damaged unexpectedly, it is important that the replacement of the damaged unit can be carried out easily. Therefore, from such a viewpoint, it is preferable to construct the casing with a pair of casing half bodies, provide each casing half body with a lubricant accommodating chamber and connect the respective casing half bodies with each other by a joint portion so that the casing can be attached or detached to/from the track shaft by opening the casing half bodies.
With such a structure, if the casing is mounted on the sliding member in such a condition that the track shaft is sandwiched by the pair of the casing half bodies, the coating pieces can be brought into contact with the track shaft, while upon replacing the lubricant supplying unit, the coating pieces can be detached from the track shaft by opening the casing half bodies, thus the lubricant supplying unit can be attached or detached to/from the sliding member not through an end of the track shaft. Consequently, if the replacement of the lubricant supplying unit is necessary because of an unexpected damage or the like, the lubricant supplying unit can be replaced without dismounting the sliding base from the track rail, thereby making it possible to carry out such a replacement work easily and at a low cost.